The present invention relates to a gate valve which may be used to remotely control the flow of fluid through various components of a flow completion system, such as a tubing hanger. More particularly, the invention relates to such a gate valve which comprises a flow-through gate and which therefore occupies a minimum of the radial cross sectional area of the component.
The need to remotely and reliably control the flow of fluid through components having relatively small radial cross sectional areas is particularly strong in the field of flow completion systems for producing oil or gas from a subsea well. For example, a typical flow completion system comprises a tubing hanger which is suspended in a wellhead housing or a tubing spool and which supports at least one tubing string that extends to the well bore. The tubing hanger includes at least one axial production bore through which the well fluids are produced, one or more service and control conduits for communicating control signals or fluids from external service and control lines to corresponding devices or positions located in or below the tubing hanger, and possibly also a longitudinal annulus bore for connecting the tubing annulus with the portion of the flow completion system that is located above the tubing hanger.
In operation of the flow completion system, flow through the annulus bore and the service and control conduits must be carefully controlled to ensure that the well fluid does not escape into the environment. However, in view of the several bores that extend through the tubing hanger, little radial cross sectional area is available for installing a standard closure member, such as a gate valve. Moreover, in the prior art a wireline plug is typically used to close the annulus bore. However, each installation or removal of the plug requires a special running trip from a surface vessel. Furthermore, although several versions of remotely operable valves for controlling flow through the tubing hanger bores have been patented, these valves have for the most part been impractical to implement due to the limited radial cross sectional area that is available in the tubing hanger for such valves.
Therefore, a need exists for a remotely operable valve which can reliably control the flow of fluid through a flow completion system component but which occupies a minimum radial cross sectional area of the component.